1. Field of the Invention
The present invention relates to an organopolysiloxane coating composition especially adapted for providing antiadhesive coatings, said composition incorporating a novel inhibitor and being particularly useful in the manufacture of paper and other substrate bearing peelable coatings.
2. Description of the Prior Art
Organopolysiloxane compositions have long been known to this art as being useful to render surfaces non-adhesive to materials to which they would normally adhere.
These known compositions incorporate:
(1) an organopolysiloxane incorporating hydrocarbon groups with aliphatic alkenyl or acetylenic unsaturation, in particular vinyl groups bonded to the silicon atoms,
(2) an organohydropolysiloxane,
(3) a catalyst of platinum group metal, and
(4) an inhibitor which retards, at ambient temperature, the bonding to a group containing aliphatic unsaturation of a hydrogen atom bonded to a silicon atom, or the reaction of a silanol group with a group .tbd.SiH.
After application to a substrate, these compositions set under the influence of an energy input by suitable treatment (heat treatment, ultraviolet (UV) or infrared ray treatment, ionizing raditation, and the like).
Such compositions, which are diluted or undiluted with a solvent, are, for example, described in French Patents Nos. 2,128,520; 2,291,254; 2,372,874; and 2,456,767.
These compositions are generally stored prior to use in the form of 2-component or 2-package compositions, the 2 components being mixed just before they are used in the form of a single composition and the principal problem to solve consists in avoiding a premature gelling of the mixture for as long a period as possible, while retaining a very good bath reactivity during the treatment for cross-linking the composition.
A great many inhibitors for the platinum group catalysts have already been proposed in the prior art, these inhibitors being capable of being employed alone or in combination and partially meeting the objectives of the present invention.
Thus, it has been proposed, in particular, to use alkylthioureas (U.S. Pat. No. 3,188,299), triallyl isocyanurates (U.S. Pat. No. 3,882,083), dialkylacetylenedicarboxylates (U.S. Pat. No. 4,347,346), a straight-chain or cyclic alkylvinylsiloxane as described in U.S. Pat. Nos. 3,516,946 and 3,775,452 and in French Patent No. 1,548,775.
U.S. Pat. No. 3,445,420 suggests, as an inhibitor, an acetylenic organic compound having a boiling point of at least 25.degree. C. and at least one group --C .tbd.C--; inhibitors of this type are also described in European Patent No. 94,185.
In French Patent No. 2,456,767 dialkyl carboxylic esters have been proposed, such as diallyl maleate.
The inhibitors of the prior art made it possible to advance the technology of the antiadhesive treatments, but they suffer from at least one of the following disadvantages:
(i) the "pot life" or "bath life" is inadequate; PA1 (ii) the inhibitors employed are toxic and/or lachrymatory and/or costly products; PA1 (iii) crosslinking must be carried out at temperatures which are too high, and/or PA1 (iv) the crosslinking is insufficient and the layer obtained does not have the intended properties.